Brain Metabolite Changes in the Anterior Cingulate Cortex of Chronic Low Back Pain Patients and Correlations Between Metabolites and Psychological State

In chronic low back pain (CLBP) patients, study of altered brain metabolites in the anterior cingulate cortex (ACC) using magnetic resonance spectroscopy (MRS) could reveal the detailed pathology of CLBP and depression. The aim was to detect the central difference between CLBP and controls by means of measuring the metabolites in the ACC, and to analyze the correlations between depression and metabolites in ACC.

MRS was performed in CLBP (n=60) and control participants (n=56) to evaluate the effects of CLBP on metabolites in the ACC and to analyze the correlations between metabolites and questionnaire scores in a cross-sectional study.

Adjusting for age and sex, a negative effect of CLBP on the N-acetylaspartate (NAA) level (estimated regression slope coefficient [B]=-0.685, P<0.001) and positive effects on the glutamate +glutamine (Glx)/creatine (B=0.136, P=0.016) and Glx/myoinositol (B=0.140, P<0.048) ratios in the ACC were found. The correlation analysis demonstrated that there was a significant moderate correlation between some questionnaire scores of emotional disorders and metabolites in the ACC of CLBP participants (absolute r>0.4, P<0.05).

Lower NAA levels and higher Glx/creatine and Glx/myoinositol ratios in the ACC of CLBP participants compared with controls were revealed. The result suggests the hypothesis that excessive Glx leads to neuronal dysfunction and/or death, which was reflected as a low NAA level in the ACC of individuals with CLBP. Measurement of these metabolites using MRS potentially helps evaluate CLBP patients' condition and psychological status objectively.