Assessment of pain due to lumbar spine diseases using MR spectroscopy: a preliminary report

BACKGROUND DATA There is a considerable difference in pain perception among individuals. In patients with chronic pain, recent studies using fMRI, PET and SPECT have shown that functional changes mainly occurred in the anterior cingulate cortex (ACC), prefrontal cortex (PFC) and thalamus. Brain magnetic resonance spectroscopy (MRS) can evaluate brain chemistry by measuring metabolites such as N-acetyl aspartate (NAA). The purpose of this study was to analyze whether brain MRS could assess pain due to lumbar spine diseases. METHODS NAA levels were determined relative to the concentration of creatine/phosphocreatine complex (Cr) and choline (Cho), which is commonly used as an internal standard. The NAA/Cr and NAA/Cho ratios in the ACC, PFC and thalamus were compared between six patients with unilateral pain (left side) and six control patients without pain. RESULTS In the right thalamus (contralateral side to symptom), the NAA/Cr in the patients with pain was statistically significantly lower compared with the control patients (p < 0.05). Also, in the right thalamus, the NAA/Cho in pain patients was significantly lower compared with controls (p < 0.01). When considering just the right thalamus, there were statistically significant correlations between the numerical rating scale for pain (NRS) and NAA values. CONCLUSIONS Lumbar pain can be assessed indirectly by analyzing the decrease in NAA concentration in the thalamus.