Quantitative meta-analysis of grey matter anomalies in neuropathic pain.

BACKGROUND: Increasing neuroimaging studies have revealed grey matter (GM) anomalies of several brain regions by voxel-based morphometry (VBM) studies in patients with neuropathic pain. The changes have been suggested to be related to central sensitization. Our aim was to investigate concurrence across VBM studies to identify whether different subtypes of neuropathic pain share a common pathophysiological basis revealed by structural abnormalities. METHODS: A systematic search of VBM studies of patients with neuropathic pain and healthy controls published in PubMed and Embase databases from January 2000 to March 2014 was conducted. A quantitative meta-analysis of whole-brain VBM studies in patients with neuropathic pain compared with healthy controls was performed by means of effect-size signed differential mapping. RESULTS: Ten studies comprising 240 patients with neuropathic pain and 263 healthy subjects were systematically included in the present study. Compared to healthy controls, the patients showed consistent decreased GM in bilateral anterior insula and thalamus, right superior frontal gyrus and left postcentral gyrus, and increased GM in right medial frontal gyrus and right posterior insula. The results remained largely unchanged in the following jackknife sensitivity analysis. CONCLUSIONS: This meta-analysis shows strong evidence of brain GM anomalies within the pain matrix in patients with neuropathic pain compared with healthy subjects. Further studies are needed to determine whether the reported changes are specific to neuropathic pain or whether they may be common to other chronic pain.

Gray matter anomalies in anterior cingulate cortex as a correlate of depressive symptoms in drug-naïve idiopathic restless legs syndrome.

BACKGROUND: Depressive symptoms are frequent in idiopathic restless legs syndrome (RLS). However, little is known, so far, about the neurological basis. The present study aimed to explore the neuroanatomical anomalies in depressed drug-naïve RLS patients using voxel-based morphometry (VBM) analysis. METHODS: We recruited 16 drug-naïve idiopathic RLS patients with depressive symptoms (RLS-D), 18 drug-naïve idiopathic RLS patients without depressive symptoms (RLS-ND), and 18 normal controls. All participants underwent structural MRI scans on a 3-T MR system. The differences in regional gray matter (GM) density were determined across groups by VBM8. Additional regression analysis was used to identify any associations between regional GM density and clinical symptoms. RESULTS: GM density of the bilateral anterior cingulate cortex (ACC) was significantly reduced in RLS-D patients when compared to RLS-ND patients or to the healthy controls. However, there were no significant differences of GM density either when the whole RLS group or the RLS-ND group was compared to healthy controls, respectively. Particularly, we found GM density of right ACC was negatively correlated with the severity and duration of depressive symptoms in RLS-D patients. CONCLUSIONS: Depressive symptoms are associated with GM anomalies in ACC in patients with RLS. We propose that ACC is perhaps an important neuroimaging marker for facilitating treatment strategies in patients with RLS when assessing depressive symptoms.