Relationship between Abnormal Spontaneous Brain Activity and Altered Neuromuscular Activation of Lumbar Paraspinal Muscles in Chronic Low Back Pain

Abstract

Abstract Background Chronic low back pain (cLBP) affects brain functional activity of the descending pain modulatory network and altered synergistic activation of lumbar paraspinal muscles. However, the neural mechanism underlying functional reorganization and effectiveness of cooperative motion remains unexplored. Methods Fifteen cLBP patients and fifteen healthy controls underwent whole brain blood oxygen level-dependent signals measured by functional magnetic resonance imaging technique and amplitude of low-frequency fluctuation (ALFF) analysis method to identify pain-induced changes in regional spontaneous brain activity. A novel approach based on the surface electromyography system and fine-wire electrodes was used to record the EMG signals in the deep multifidus, superficial multifidus and erector spinae. Results ALFF was higher in the medial prefrontal cortex, primary somatosensory cortex, motor cortex and inferior temporal cortex in cLBP than at the baseline, whereas lower in the cerebellum, anterior cingulate cortex and posterior cingulate cortex. Further, the decrease in the average electromyography of three lumbar muscles in the cLBP group was positively correlated with the ALFF values of the primary somatosensory cortex, motor cortex, precuneus and middle temporal cortex, but significantly negatively correlated with the medial prefrontal cortex and inferior temporal cortex. Interestingly, the correlation between the functional activity in the cerebellum and the electromyography activity varied in lumbar muscles. Conclusion These findings suggest a functional association between abnormal spontaneous brain activity and altered voluntary neuromuscular activation patterns of the lumbar paraspinal muscles, providing new insights into the underlying mechanisms of pain chronicity and important implications for developing novel therapeutic targets of cLBP patients.