title: Motor cortical activity during motor tasks is normal in patients with complex regional pain syndrome.
abstract: Motor dysfunction in complex regional pain syndrome (CRPS) is often considered a functional movement disorder. Earlier studies in patients with functional movement disorders found evidence of cortical inhibition during explicit but not implicit motor tasks, suggesting active inhibition from other brain areas. In this study, we explored whether active inhibition occurs in CRPS patients. We compared patients with CRPS with 2 control groups: healthy controls matched for age and sex, and patients whose hand was immobilized to treat a scaphoid fracture. We used transcranial magnetic stimulation to measure corticospinal excitability at rest and during motor imagery (explicit motor task) and motor observation (implicit motor task). Motor corticospinal excitation measured at rest and during implicit and explicit motor tasks was similar for CRPS patients and healthy controls. Patients with an immobilized hand showed an absence of motor cortical excitation of the corresponding hemisphere during motor imagery of tasks involving the immobilized hand, but not during motor observation. The normal motor cortical processing during motor imagery and motor observation found in the corresponding hemisphere of CPRS patients suggests that the nature of motor dysfunction in this condition differs from that described in literature for patients with functional paresis or under circumstances of limb immobilization.
  
  
  CONCLUSIONS
  This study shows that the nature of motor dysfunction in CRPS patients differs from that encountered in patients with functional paresis or under circumstances of limb immobilization. This information is important for patients and pain clinicians and could help prevent implementation of therapeutic strategies based on incorrect assumptions.
authors.affiliation: Department of Neurology, Leiden University Medical Centre, Leiden, The Netherlands; Knowledge Consortium TREND, Leiden, The Netherlands. Electronic address: g.a.j.van_velzen@lumc.nl.
authors.forename: Gijsbrecht A J
authors.initials: GA
authors.lastname: van Velzen
authors.affiliation: Department of Neurology, Leiden University Medical Centre, Leiden, The Netherlands; Knowledge Consortium TREND, Leiden, The Netherlands.
authors.forename: Johan
authors.initials: J
authors.lastname: Marinus
authors.affiliation: Department of Neurology, Leiden University Medical Centre, Leiden, The Netherlands.
authors.forename: J Gert
authors.initials: JG
authors.lastname: van Dijk
authors.affiliation: Department of Medical Statistics and BioInformatics, Leiden University Medical Centre, Leiden, The Netherlands.
authors.forename: Erik W
authors.initials: EW
authors.lastname: van Zwet
authors.affiliation: Department of Surgery and Trauma Surgery, Leiden University Medical Centre, Leiden, The Netherlands.
authors.forename: Inger B
authors.initials: IB
authors.lastname: Schipper
authors.affiliation: Department of Neurology, Leiden University Medical Centre, Leiden, The Netherlands; Knowledge Consortium TREND, Leiden, The Netherlands.
authors.forename: Jacobus J
authors.initials: JJ
authors.lastname: van Hilten
mesh_terms: D000328:Adult; D020918:Complex Regional Pain Syndromes / Q000503:physiopathology*; D016267:External Fixators; D005260:Female; D007839:Functional Laterality; D006225:Hand / Q000503:physiopathology; D006801:Humans; D007092:Imagination / Q000502:physiology*; D007103:Immobilization; D008297:Male; D008875:Middle Aged; D009039:Motion Perception / Q000502:physiology*; D009043:Motor Activity / Q000502:physiology*; D009044:Motor Cortex / Q000503:physiopathology*; D012146:Rest; D021361:Scaphoid Bone / Q000293:injuries; D050781:Transcranial Magnetic Stimulation; D055815:Young Adult
keywords: Complex regional pain syndrome; cortical excitability; psychogenic; transcranial magnetic stimulation