Change of cerebral metabolites and activated region by lumbar mechanical stimulus in the patient with chronic low back pain

Abstract

Studies of brain imaging in chronic low back pain (CLBP) patients have been recently increased. First, MR spectroscopy (MRS) was performed in CLBP patients (n=60) and control subjects (n=56) to evaluate the effects of CLBP on metabolites in the anterior cingulate cortex (ACC). Negative effects of CLBP on the N-acetyl aspartate (NAA) levels and positive effects on the glutamate + glutamine / creatine (Glx / Cr) ratios in the ACC were found. 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 CLBP patients. Second, The NAA / Cr and NAA / choline ratios in the thalamus were compared between 6 patients with the left side of unilateral pain and 6 control patients. In the right thalamus, the NAA / Cr in the patients with pain was significantly lower compared with the control patients, and there were significant correlations between the numerical rating scale (NRS) and NAA levels. Lumbar pain can be assessed indirectly by analyzing the decrease in NAA concentration in the thalamus. Third, to explore a pathologic pattern of cerebral activation in chronic LBP patients, 8 healthy volunteers and 6 patients with idiopathic, chronic LBP were recruited and performed functional MRI (fMRI). Each subject was placed in the prone position on a 3 Tesla MRI scanner, and performed lumbar mechanical stimulus. The pressure was established at either 3 or 5 on the 10-cm visual analog scale (VAS) using 25-ml syringe. Pain thresholds were smaller than in healthy subjects. LBP patients showed augmented activation compared with healthy volunteers specifically at the right insula, supplementary motor, and PCC. Chronic LBP patients showed increased tenderness at the lower back and augmented cerebral activation. The LBP-related activation is characterized by the absence of sensory-discriminative component. Fourth, 21 patients with cLBP were recruited and divided into two groups on the basis of scores on the patient version of the Brief Scale for Psychiatric problems in Orthopaedic Patients (BS-POP) scores: >= 17 (high-score group) and <17 (non-high-score group). Subjects in the high-score group had more intense daily pain and lower quality of life than those in the non-high-score group. Activation at the nucleus accumbens (NAc) was smaller in the high-score group than in the non-high-score group. The presence of psychiatric problems was associated with attenuated activity of the NAc in cLBP patients.