Table 1.
Clinical features of CRPS patients.
Figure 1.
Comparing CRPS patients to age and gender matched controls by VBM whole brain analysis identified one significant cluster with increased gray matter density in CRPS patients located in the DMPFC (peak voxel-level: 1.5, 52.5, 16.5 (x, y, z, mm), T = 4.42, p<0.001 uncorrected, cluster-level: 556 voxels, p = 0.03 FWE corrected).
Since we found no link to the individual clinical CRPS features (see Results), the interpretation of this finding remains speculative, but it may point to pain associated altered cognitive processes such as emotional suffering. The bar plot represents estimated gray matter density from the peak voxel. The whiskers indicate the standard error.
Table 2.
Overview on gray and white matter findings when comparing CRPS patients to age and gender matched healthy control subjects (DMPFC: dorsomedial prefrontal cortex; M1: primary motor cortex; S1: primary somatosensory cortex).
Figure 2.
To identify structural changes in the somatosensory cortex, MRI scans of patients with left-sided CRPS were horizontally flipped before data pre-processing and statistical comparison (i.e., CRPS > controls).
Using small volume correction we found one significant cluster with increased gray matter density, which was located in the primary motor cortex (M1: peak voxel-level: –40.5, –9, 60 (x, y, z, mm), T = 4.31, p<0.001 uncorrected, cluster-level: 89 voxels, p = 0.042 FWE corrected). As for the DMPFC (see Fig. 1), we found no correlation between altered grey matter density in primary motor cortex and clinical CRPS features (see Results). The bar plot shows estimated gray matter density of the peak voxel and whiskers indicate standard error.
Figure 3.
Voxel-wise VBM statistics of whole brain white matter structure revealed one significant cluster with decreased white matter density when comparing CRPS patients to matched controls (see blue cluster, peak voxel-level:–21, 3, 4.5 (x, y, z, mm), T = 4.07, p<0.001 uncorrected, cluster-level: 789 voxels, p = 0.014 FWE corrected).
This cluster was located in the internal capsule, known to contain the projections from the M1 to the brainstem. In agreement with this anatomical implementation, we found that reduced individual white matter density negatively correlated (see scatter plot) with increased gray matter density we found in primary motor cortex (M1, see red cluster and Fig. 2). The red diamonds indicate patients with left-sided CRPS. Bar plot indicates estimated gray matter changes of the peak voxel; whiskers the standard error.
Figure 4.
Unlike the correlation we found between gray matter structure in the M1 and the internal capsule, we found no correlation with gray matter density in the DMPFC.