title: The role of periaqueductal gray and cingulate cortex during suppression of pain in complex regional pain syndrome.
abstract: OBJECTIVE
  Complex regional pain syndrome I (CRPS I) is a frequent and debilitating condition with unclear etiology. Hypothesizing that maladaptive central processes play a crucial role in CRPS, the current study set out to explore cerebral activation during a task to suppress the feeling of pain under constant painful stimulation.
  
  
  METHODS
  Ten individuals with CRPS I with symptoms on their left hand were subjected to electrical stimulation of both index fingers subsequently in a functional magnetic resonance imaging experiment. Their data were compared with 15 healthy controls.
  
  
  RESULTS
  Concerning psychophysical measures, patients succeeded similarly as healthy controls in suppressing the feeling of pain. However, during constant painful stimulation and with the task to suppress the feeling of pain, there were significant differences in the interaction analyses of the corresponding cortical activation.
  
  
  CONCLUSIONS
  Patients differ from healthy controls by the activation pattern of cerebral areas that belong to the descending opioid pain suppression pathway: PAG and cingulate cortex are activated significantly less during suppression of pain, regardless of whether the symptomatic or asymptomatic hand was stimulated. Thus, there is a generalized functional change in individuals with CRPS I. However, it cannot be deducted whether the abnormality is causative or merely an effect, possibly maladaptive.
authors: Department of Diagnostic and Interventional Radiology, University Hospital Ulm, Germany. freund-ulm@t-online.de
authors: Wolfgang
authors: W
authors: Freund
authors: Arthur P
authors: AP
authors: Wunderlich
authors: Gregor
authors: G
authors: Stuber
authors: Florian
authors: F
authors: Mayer
authors: Peter
authors: P
authors: Steffen
authors: Martin
authors: M
authors: Mentzel
authors: Bernd
authors: B
authors: Schmitz
authors: Frank
authors: F
authors: Weber