Altered low-frequency oscillation amplitude of resting state-fMRI in patients with discogenic low-back and leg pain

The aim of this study was to explore the amplitude of intrinsic low-frequency oscillations (LFOs) in patients with discogenic low-back and leg pain (LBLP).

We obtained and compared the LFO amplitude from 25 right-handed discogenic LBLP patients (13 males; mean age 55.16±1.83 years) and 27 well-matched healthy controls (15 males; mean age 52.96±1.63 years). The LFO amplitude was examined using the voxel-wise amplitude of low-frequency fluctuations (ALFFs), and partial correlation analysis was performed to determine the relationship between the regions with altered ALFF values and clinical parameters in discogenic LBLP patients.

Compared with healthy controls, the patients with discogenic LBLP showed a significant increase in ALFF in the affective system of the pain matrix (left anterior cingulate cortex, right anterior insula/frontal operculum, and bilateral orbitofrontal cortex) and information-processing regions (middle occipital/temporal gyrus). In addition, a significant decrease in ALFF was observed in the default mode network (DMN; inferior parietal lobule (IPL) and medial prefrontal cortex [mPFC]) and the processing system of the pain matrix (basal ganglia/thalamus/midbrain, postcentral gyrus [PoCG], and fusiform gyrus). Several regions with altered ALFF were associated with disease duration, visual analog scale scores, Barthel index, and fine sensory modality measurements (two-point tactile discrimination of the left and/or right leg). Further operating characteristic curves analysis suggested that the mean ALFF values in the right IPL, left IPL/PoCG, left anterior cingulate cortex, and left mPFC could serve as markers to separate individuals with discogenic LBLP from healthy subjects.

Our results revealed widespread abnormalities in ALFF in the pain matrix and information-processing regions as well as a decrease in ALFF in the DMN. These results open up an important new avenue to better understand the nature of the link between intrinsic activity and peripheral pain and sensory impairment in discogenic LBLP patients.