Current source density and functional connectivity extracted from resting-state electroencephalography as biomarkers for chronic low back pain

Abstract

Introduction: Chronic low back pain (CLBP) is a global health issue, and its nonspecific causes make treatment challenging. Understanding the neural mechanisms of CLBP should contribute to developing effective therapies.

Objectives: To compare current source density (CSD) and functional connectivity (FC) extracted from resting electroencephalography (EEG) between patients with CLBP and healthy controls and to examine the correlations between EEG indices and symptoms.

Methods: Thirty-four patients with CLBP and 34 healthy controls in an open data set were analyzed. Five-minute resting-state closed-eye EEG was acquired using the international 10-20 system. Current source density across frequency bands was calculated using exact low-resolution electromagnetic tomography. Functional connectivity was assessed between 24 cortical regions using lagged linear connectivity. Correlations between pain symptoms and CSD distribution and FC were examined in patients with CLBP.

Results: Current source density analysis showed no significant differences between the groups. The CLBP group exhibited significantly reduced FC in the β3 band between the left middle temporal gyrus and the posterior cingulate cortex, and between the ventral medial prefrontal cortex and the left inferior parietal lobule. Prefrontal θ and δ activity positively correlated with pain symptoms. Increased β1 band FC between the right dorsolateral prefrontal cortex and right auditory cortex correlated with greater pain intensity.

Conclusions: We found altered neural activity and connectivity in patients with CLBP, particularly in prefrontal and temporal regions. These results suggest potential targets for pain modulation through brain pathways and highlight the value of EEG biomarkers in understanding pain mechanisms and assessing treatment efficacy.

Keywords: Biomarker; Chronic low back pain; Chronic pain; Electroencephalogram; Resting state.

Figure 1.

Averaged exact low resolution electromagnetic tomography CSD for each frequency band in the CLBP and HC groups. The color scale shows CSD from 0.000 (black) to 0.200 (red). Statistical analysis showed no significant differences between the 2 groups. CLBP, chronic low back pain; CSD, current source density; HC, healthy control.

Figure 2.

Exact low resolution electromagnetic tomography wire diagram indicating significantly reduced FC in the CLBP group compared with the HC group. The 2 blue lines indicate significant lower FCs in the β3 band (21.5–30 Hz) in the CLBP group compared with the HC group. One of the lines is between the left middle temporal gyrus–posterior cingulate cortex, and the other is between ventral medial prefrontal cortex–left inferior parietal lobule. CLBP, chronic low back pain; FC, functional connectivity; HC, healthy control.

Figure 3.

Exact low resolution electromagnetic tomography maps showing cortical regions that have a significant positive correlation with θ band CSD value and SF-MPQ total score. The voxels with θ band CSD value that showed a significant positive correlation with the SF-MPQ total score are colored. Significant positive correlation localizations are present in the left-side dominant prefrontal cortex. The image above shows the voxels indicated when the P value is set to 0.05 or less, colored yellow, and the image below shows the voxels indicated when the P value is set to 0.10 or less, colored red. CSD, current source density; SF-MPQ, Short Form McGill Pain Questionnaire.

Figure 4.

Exact low resolution electromagnetic tomography maps indicating cortical regions that have significant correlations with delta band CSD value and current pain intensity. The voxels that showed a significant positive correlation with the current pain intensity in the delta band CSD values are colored. Significant positive correlation localizations are present in the left prefrontal cortex. The image above shows the voxels indicated when the P value is set to 0.05 or less, colored yellow, and the image below shows the voxels indicated when the P value is set to 0.10 or less, colored red. CSD, current source density.

Figure 5.

Exact low resolution electromagnetic tomography wire diagram indicating FC that showed significant correlations with current pain intensity. The red line indicates the β1 band (12.5–18.0 Hz) FC that was significantly positively correlated with current pain intensity. The line connects the right dorsolateral prefrontal cortex and the right auditory cortex. FC, functional connectivity.