title: Primary somatosensory cortex function in complex regional pain syndrome: a systematic review and meta-analysis.
abstract: That complex regional pain syndrome (CRPS) is associated with functional reorganization in the primary somatosensory cortex (S1) is widely accepted and seldom questioned. Despite more than a decade of research, there has been no systematic review of the CRPS literature concerning the changes in S1 function, and therefore the extent of these changes is unclear. Here we conduct a systematic review and meta-analysis to quantify the spatial and temporal aspects of S1 function in CRPS. A comprehensive search strategy identified functional neuroimaging studies of S1 in CRPS. We adhered to a rigorous systematic review protocol when extracting data and appraising risk of bias. Outcomes were grouped into spatial representation; activation levels, including disinhibition; peak latency of activation; and glucose metabolism. Meta-analysis was conducted where possible. Fifteen studies were included, all investigating upper-extremity CRPS. In patients with CRPS, the S1 spatial representation of the affected hand is smaller than that of the unaffected hand and that of non-CRPS controls; however, this evidence comes from only a few studies. There is no difference in activation, disinhibition, or latency of peripherally evoked S1 responses in CRPS. The risk of bias was high across studies, mainly from unclear sampling methods and unblinded analysis of outcomes.
  
  
  CONCLUSIONS
  The evidence for a difference in function of the primary somatosensory cortex in CRPS compared with controls is clouded by high risk of bias and conflicting results, but reduced representation size seems consistent.
authors.affiliation: Neuroscience Research Australia, Sydney, Australia; Prince of Wales Clinical School, University of New South Wales, Sydney, Australia.
authors.forename: Flavia
authors.initials: F
authors.lastname: Di Pietro
authors.forename: James H
authors.initials: JH
authors.lastname: McAuley
authors.forename: Luke
authors.initials: L
authors.lastname: Parkitny
authors.forename: Martin
authors.initials: M
authors.lastname: Lotze
authors.forename: Benedict M
authors.initials: BM
authors.lastname: Wand
authors.forename: G Lorimer
authors.initials: GL
authors.lastname: Moseley
authors.forename: Tasha R
authors.initials: TR
authors.lastname: Stanton
mesh_terms: D000328:Adult; D000368:Aged; D020918:Complex Regional Pain Syndromes / Q000503:physiopathology*; D003627:Data Interpretation, Statistical; D005260:Female; D005947:Glucose / Q000378:metabolism; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D010147:Pain Measurement; D017594:Publication Bias; D013003:Somatosensory Cortex / Q000503:physiopathology*; D055815:Young Adult
chemical_list: D005947:Glucose
keywords: Complex regional pain syndrome; S1; cortical reorganization; neuroimaging; primary somatosensory cortex