Fig. 2

Results of the statistical parametric mapping (SPM) analysis showing brain regions with significant rCBF changes in 14 patients with CLBP, compared to ten healthy controls. The figure shows the overlay of clusters upon T1-weighted magnetic resonance imaging from the SPM template. Images show areas with a significant increase (A, B, D, and E) and decrease (C and F) of the regional cerebral blood flow (rCBF). The significant increase of rCBF was found in clusters A (3D view in D; R occipital lobe and R posterior cingulate gyrus) and B (3D view in E; R anterior prefrontal and dorsolateral frontal lobe). Cluster C presented a decrease of rCBF (3D view in F; bilateral parasagittal and postcentral parietal lobe and R middle cingulate cortex). Table 2 describes the Talairach coordinates. Results are shown in p value less than 0.05, corrected for multiple comparisons. A correlation coefficient with 95% CI according to Kendall’s tau non-parametric rank correlation was used to assess the relationship between the rCBF increase (a, b, d, and e) and decrease (c and f) and the results of the NRS (a–c) and DN4 (d–f) scores. The curved lines show the 95% CI around the regression line. In b, higher NRS scores were inversely and moderately correlated with the intensity of rCBF increase in cluster B (Kendall’s tau =  − 0.445, p = 0.033). In a, c, d, e, and f, there was no significant correlation between rCBF changes and NRS or DN4 scores. NRS Numeric Rating Scale; DN4 Douleur Neuropathique en 4 Questions